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Memory efficient xcontent filtering (backport of elastic#77154)
I found myself needing support for something like `filter_path` on `XContentParser`. It was simple enough to plug it in so I did. Then I realized that it might offer more memory efficient source filtering (elastic#25168) so I put together a quick benchmark comparing the source filtering that we do in `_search`. Filtering using the parser is about 33% faster than how we filter now when you select a single field from a 300 byte document: ``` Benchmark (excludes) (includes) (source) Mode Cnt Score Error Units FetchSourcePhaseBenchmark.filterObjects message short avgt 5 2360.342 ± 4.715 ns/op FetchSourcePhaseBenchmark.filterXContentOnBuilder message short avgt 5 2010.278 ± 15.042 ns/op FetchSourcePhaseBenchmark.filterXContentOnParser message short avgt 5 1588.446 ± 18.593 ns/op ``` The top line is the way we filter now. The middle line is adding a filter to `XContentBuilder` - something we can do right now without any of my plumbing work. The bottom line is filtering on the parser, requiring all the new plumbing. This isn't particularly impresive. 33% *sounds* great! But 700 nanoseconds per document isn't going to cut into anyone's search times. If you fetch a thousand docuents that's .7 milliseconds of savings. But we mostly advise folks to use source filtering on fetch when the source is large and you only want a small part of it. So I tried when the source is about 4.3kb and you want a single field: ``` Benchmark (excludes) (includes) (source) Mode Cnt Score Error Units FetchSourcePhaseBenchmark.filterObjects message one_4k_field avgt 5 5957.128 ± 117.402 ns/op FetchSourcePhaseBenchmark.filterXContentOnBuilder message one_4k_field avgt 5 4999.073 ± 96.003 ns/op FetchSourcePhaseBenchmark.filterXContentonParser message one_4k_field avgt 5 3261.478 ± 48.879 ns/op ``` That's 45% faster. Put another way, 2.7 microseconds a document. Not bad! But have a look at how things come out when you want a single field from a 4 *megabyte* document: ``` Benchmark (excludes) (includes) (source) Mode Cnt Score Error Units FetchSourcePhaseBenchmark.filterObjects message one_4m_field avgt 5 8266343.036 ± 176197.077 ns/op FetchSourcePhaseBenchmark.filterXContentOnBuilder message one_4m_field avgt 5 6227560.013 ± 68306.318 ns/op FetchSourcePhaseBenchmark.filterXContentonParser message one_4m_field avgt 5 1617153.472 ± 80164.547 ns/op ``` These documents are very large. I've encountered documents like them in real life, but they've always been the outlier for me. But a 6.5 millisecond per document savings ain't anything to sneeze at. Take a look at what you get when I turn on gc metrics: ``` FetchSourcePhaseBenchmark.filterObjects message one_4m_field avgt 5 7036097.561 ± 84721.312 ns/op FetchSourcePhaseBenchmark.filterObjects:·gc.alloc.rate message one_4m_field avgt 5 2166.613 ± 25.975 MB/sec FetchSourcePhaseBenchmark.filterXContentOnBuilder message one_4m_field avgt 5 6104595.992 ± 55445.508 ns/op FetchSourcePhaseBenchmark.filterXContentOnBuilder:·gc.alloc.rate message one_4m_field avgt 5 2496.978 ± 22.650 MB/sec FetchSourcePhaseBenchmark.filterXContentonParser message one_4m_field avgt 5 1614980.846 ± 31716.956 ns/op FetchSourcePhaseBenchmark.filterXContentonParser:·gc.alloc.rate message one_4m_field avgt 5 1.755 ± 0.035 MB/sec ```
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...ain/java/org/elasticsearch/benchmark/search/fetch/subphase/FetchSourcePhaseBenchmark.java
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,138 @@ | ||
| package org.elasticsearch.benchmark.search.fetch.subphase; | ||
|
|
||
| import org.elasticsearch.common.Strings; | ||
| import org.elasticsearch.common.bytes.BytesArray; | ||
| import org.elasticsearch.common.bytes.BytesReference; | ||
| import org.elasticsearch.common.io.Streams; | ||
| import org.elasticsearch.common.io.stream.BytesStreamOutput; | ||
| import org.elasticsearch.common.xcontent.DeprecationHandler; | ||
| import org.elasticsearch.common.xcontent.NamedXContentRegistry; | ||
| import org.elasticsearch.common.xcontent.XContentBuilder; | ||
| import org.elasticsearch.common.xcontent.XContentParser; | ||
| import org.elasticsearch.common.xcontent.XContentType; | ||
| import org.elasticsearch.common.xcontent.support.filtering.FilterPath; | ||
| import org.elasticsearch.search.fetch.subphase.FetchSourceContext; | ||
| import org.elasticsearch.search.fetch.subphase.FetchSourcePhase; | ||
| import org.elasticsearch.search.lookup.SourceLookup; | ||
| import org.openjdk.jmh.annotations.Benchmark; | ||
| import org.openjdk.jmh.annotations.BenchmarkMode; | ||
| import org.openjdk.jmh.annotations.Fork; | ||
| import org.openjdk.jmh.annotations.Measurement; | ||
| import org.openjdk.jmh.annotations.Mode; | ||
| import org.openjdk.jmh.annotations.OutputTimeUnit; | ||
| import org.openjdk.jmh.annotations.Param; | ||
| import org.openjdk.jmh.annotations.Scope; | ||
| import org.openjdk.jmh.annotations.Setup; | ||
| import org.openjdk.jmh.annotations.State; | ||
| import org.openjdk.jmh.annotations.Warmup; | ||
|
|
||
| import java.io.IOException; | ||
| import java.util.Set; | ||
| import java.util.concurrent.TimeUnit; | ||
|
|
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| @Fork(1) | ||
| @Warmup(iterations = 5) | ||
| @Measurement(iterations = 5) | ||
| @BenchmarkMode(Mode.AverageTime) | ||
| @OutputTimeUnit(TimeUnit.NANOSECONDS) | ||
| @State(Scope.Benchmark) | ||
| public class FetchSourcePhaseBenchmark { | ||
| private BytesReference sourceBytes; | ||
| private FetchSourceContext fetchContext; | ||
| private Set<String> includesSet; | ||
| private Set<String> excludesSet; | ||
| private FilterPath[] includesFilters; | ||
| private FilterPath[] excludesFilters; | ||
|
|
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| @Param({ "tiny", "short", "one_4k_field", "one_4m_field" }) | ||
| private String source; | ||
| @Param({ "message" }) | ||
| private String includes; | ||
| @Param({ "" }) | ||
| private String excludes; | ||
|
|
||
| @Setup | ||
| public void setup() throws IOException { | ||
| switch (source) { | ||
| case "tiny": | ||
| sourceBytes = new BytesArray("{\"message\": \"short\"}"); | ||
| break; | ||
| case "short": | ||
| sourceBytes = read300BytesExample(); | ||
| break; | ||
| case "one_4k_field": | ||
| sourceBytes = buildBigExample("huge".repeat(1024)); | ||
| break; | ||
| case "one_4m_field": | ||
| sourceBytes = buildBigExample("huge".repeat(1024 * 1024)); | ||
| break; | ||
| default: | ||
| throw new IllegalArgumentException("Unknown source [" + source + "]"); | ||
| } | ||
| fetchContext = new FetchSourceContext( | ||
| true, | ||
| Strings.splitStringByCommaToArray(includes), | ||
| Strings.splitStringByCommaToArray(excludes) | ||
| ); | ||
| includesSet = Set.of(fetchContext.includes()); | ||
| excludesSet = Set.of(fetchContext.excludes()); | ||
| includesFilters = FilterPath.compile(Set.of(fetchContext.includes())); | ||
| excludesFilters = FilterPath.compile(Set.of(fetchContext.excludes())); | ||
| } | ||
|
|
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| private BytesReference read300BytesExample() throws IOException { | ||
| return Streams.readFully(FetchSourcePhaseBenchmark.class.getResourceAsStream("300b_example.json")); | ||
| } | ||
|
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| private BytesReference buildBigExample(String extraText) throws IOException { | ||
| String bigger = read300BytesExample().utf8ToString(); | ||
| bigger = "{\"huge\": \"" + extraText + "\"," + bigger.substring(1); | ||
| return new BytesArray(bigger); | ||
| } | ||
|
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| @Benchmark | ||
| public BytesReference filterObjects() throws IOException { | ||
| SourceLookup lookup = new SourceLookup(); | ||
| lookup.setSource(sourceBytes); | ||
| Object value = lookup.filter(fetchContext); | ||
| return FetchSourcePhase.objectToBytes(value, XContentType.JSON, Math.min(1024, lookup.internalSourceRef().length())); | ||
| } | ||
|
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| @Benchmark | ||
| public BytesReference filterXContentOnParser() throws IOException { | ||
| BytesStreamOutput streamOutput = new BytesStreamOutput(Math.min(1024, sourceBytes.length())); | ||
| XContentBuilder builder = new XContentBuilder(XContentType.JSON.xContent(), streamOutput); | ||
| try ( | ||
| XContentParser parser = XContentType.JSON.xContent() | ||
| .createParser( | ||
| NamedXContentRegistry.EMPTY, | ||
| DeprecationHandler.THROW_UNSUPPORTED_OPERATION, | ||
| sourceBytes.streamInput(), | ||
| includesFilters, | ||
| excludesFilters | ||
| ) | ||
| ) { | ||
| builder.copyCurrentStructure(parser); | ||
| return BytesReference.bytes(builder); | ||
| } | ||
| } | ||
|
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| @Benchmark | ||
| public BytesReference filterXContentOnBuilder() throws IOException { | ||
| BytesStreamOutput streamOutput = new BytesStreamOutput(Math.min(1024, sourceBytes.length())); | ||
| XContentBuilder builder = new XContentBuilder( | ||
| XContentType.JSON.xContent(), | ||
| streamOutput, | ||
| includesSet, | ||
| excludesSet, | ||
| XContentType.JSON.toParsedMediaType() | ||
| ); | ||
| try ( | ||
| XContentParser parser = XContentType.JSON.xContent() | ||
| .createParser(NamedXContentRegistry.EMPTY, DeprecationHandler.THROW_UNSUPPORTED_OPERATION, sourceBytes.streamInput()) | ||
| ) { | ||
| builder.copyCurrentStructure(parser); | ||
| return BytesReference.bytes(builder); | ||
| } | ||
| } | ||
| } |
20 changes: 20 additions & 0 deletions
20
...ks/src/main/resources/org/elasticsearch/benchmark/search/fetch/subphase/300b_example.json
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|---|---|---|
| @@ -0,0 +1,20 @@ | ||
| { | ||
| "@timestamp": "2099-11-15T14:12:12", | ||
| "http": { | ||
| "request": { | ||
| "method": "get" | ||
| }, | ||
| "response": { | ||
| "bytes": 1070000, | ||
| "status_code": 200 | ||
| }, | ||
| "version": "1.1" | ||
| }, | ||
| "message": "GET /search HTTP/1.1 200 1070000", | ||
| "source": { | ||
| "ip": "192.168.0.1" | ||
| }, | ||
| "user": { | ||
| "id": "user" | ||
| } | ||
| } |
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